Add olive oil to an oven-safe skillet over medium high heat until it just starts to smoke. Add sausage, chicken, onions, and bell peppers. Season with cajun seasoning (about 1-2 teaspoons). Cook until lightly browned. Add garlic stir to combine until fragrant, about 30 seconds.Add the broth, cream, pasta, and more cajun seasoning to taste, about ½ teaspoon. Stir to combine and bring to a boil, then cover skillet and reduce heat to medium-low. Simmer until pasta is tender, about 15 minutes.Remove skillet from heat and stir in ½ cup cheese. Top with remaining cheese and sprinkle with scallions. Broil until cheese is melted, golden brown, and bubbly.